In the system disclosed in Patent Literature 1, a volume is composed of one or more tracks. In a real storage apparatus, each track includes a home address and Record 0 at the beginning of the track and records (Record 1, Record 2 . . . ) for storing user data subsequent to the Record 0. An MF (Main Frame) host defines a dataset in a VTOC (Volume Table of Contents) and creates records in a track to be allocated for the dataset.
The MF host writes user data to the records in the track to update the records. If the records created in the track have equal lengths, a storage system calculates write positions in the records and carries out a cache write.
In the storage system disclosed in Patent Literature 2 manages virtual volumes composed of virtual storage areas and allocates a real storage area to a virtual volume in response to a host write. When an MF host defines a dataset in a virtual volume, a storage system allocates a real storage area to the virtual volume through the above-described record creation.